Automotive vehicles that are powered by internal combustion engines are required to comply with certain laws and regulations relating to exhaust emissions. Mandated requirements presently and prospectively include limits on certain noxious constituents in emitted exhaust gas and on-board diagnostic systems for detecting non-compliance. In fact, one prospective requirement is that a non-compliant fuel injector for an engine cylinder be shut off until the vehicle can be serviced for corrective action.
When an automotive vehicle is operating with its engine in compliance, it is expected that each one of its combustion chambers is individually operating in compliance. Non-compliant operation of an individual combustion chamber may occur for any of a number of different reasons including reasons other than a non-compliant fuel injector.
Other engine events which are apt to contribute to non-compliance may include, by way of example, failure of the ignition system to properly ignite combustible mixture in a combustion chamber, and failure of an EVT system to properly operate a valve. The root cause of any non-compliant operation may be due to non-compliant operation of any one or more of a number of individual components, such as fuel injectors, spark plugs, electronics, sensors, actuators, etc.
It is known to equip a spark-ignited internal combustion engine with electromechanically actuated cylinder valves which are under the control of an EVT system. The typical electromechanical actuator is solenoid-actuated. An example of an EVT system is disclosed in commonly assigned U.S. Pat. No. 4,957,074.
The present invention relates to an improvement in an EVT-equipped engine and is especially useful in alleviating effects of non-compliance in the operation of an individual combustion chamber. For example, an event of non-compliance that is limited to a single combustion chamber may be sufficient to cause the vehicle to become non-compliant, yet may go unnoticed by the vehicle operator. Other events of non-compliance may have the potential for damaging the engine and/or related systems, and may even detrimentally escalate if not promptly corrected.
A specific example of an effect of non-compliant operation of an individual combustion chamber is illustrated by an engine whose air-fuel mixture is controlled by an oxygen sensor in the exhaust. If the air-fuel mixture in that combustion chamber is improperly prepared and/or combusted, the resulting constituents in the combusted mixture will have an influence on the oxygen sensor indicating that the mixture is either too rich or too lean. The engine management computer will respond by altering the operation in a manner which will tend to compensate for the detected change. This, however, will result in corrective action being taken to compliantly operating combustion chambers with attendant liklihood of augmenting, rather than alleviating, the problem. For example, failure of a fuel injector which requires, under the aforementioned prospective requirement, that the fuel injector be shut off in order to minimize pollution effects pending servicing, will result in air being pumped from that cylinder into the exhaust. The consequent lean bias in the exhaust is detected by the oxygen sensor and results in the engine management computer either falsely shifting the mixture or forcing the operating mode from closed-loop to open-loop, impairing catalyst subsystem efficiency or even rendering the catalyst ineffective.
In general, the present invention proposes a solution to the aforementioned deficiencies by deactivating the intake valve of the non-compliantly operating combustion chamber upon detection of non-compliant operation so that the associated intake valve is kept closed. In this way, fresh charges of combustible mixture are prevented from entering the combustion chamber. So long as the engine is equipped with a sufficient number of combustion chambers, the vehicle can continue to be operated although it is to be expected that the operator will perceive that the engine is not operating properly. By taking this corrective action however, the compliant combustion chambers remain unaffected, and consequently, the effect of the non-compliant combustion chamber on exhaust emission constituents is ameliorated from what would otherwise have been the case if such corrective action had not been taken. Deactivation of the non-compliant combustion chamber's intake valve is accomplished by prohibiting its solenoid from being electrically operated to open the intake valve.
In its broadest sense the invention contemplates that the corrective action of deactivating a non-compliant cylinder's intake valve can be performed in response to detection of various forms of evidence of non-compliance. For instance, one or more inputs such as engine roughness at idle, manifold pressure, engine knock, are possibilities that are additional and/or alternative to the use of the oxygen sensor in this specific example described in the preceding paragraph. Events indicative of non-compliance can be logged in storage of the engine management computer in conventional fashion, such as by setting flags or semifore.
Further aspects of the invention along with those already mentioned will be described in the ensuing detailed description of a presently preferred embodiment representing the best mode contemplated at this time for carrying out the invention.